The purposes of this study is to develop parent report and observational measures for the following temperament dimensions: activity level, general positive intensity, general negative intensity, fear, adaptability, rhythmicity, distractibility, persistence, attachment and anger/ frustration, and to cross-validate the measures on a group of 50 subjects at 3, 6, and 9 months of age. Four-hundred-fifty parents of infants aged 3 to 12 months have now filled out the preliminary parent report instrument; item analyses have been performed and scales refined. Observational codes of temperament variables have also been developed, and parent-report and observational measures will be cross-validated in our next phase of research. Intra-individual stability of temperament measures from 3 to 9 months, sex and birth order differences will also be examined.